I would assume this is not Stema's fault and actually on yuor side, you can try: Right click on the headphones icon in the tray bar, select recording devices and click listen in the top bar, then un-select "Listen to this device" and click apply and OK, this should be fixed, if it still carrys on, try to move away your mic away from your speakers, if you have headphones with an mic that sticks out, try to lower your volume down. If all these fail then it's something on Steam's side.